Electric furnace



M. R.TREMBOUR.

ELECTRIC FURNACE,

APPLICATION FILED 007.1.1919.

1,369,578. Patented Feb.- 22,1921.

'w INVENTOIR Max 7?.TREMB0U'R UNITED STATES PATENT OFFICE.

MAX R. TREMBOUR, OF TROY, NEW YORK, ASSIG-NDR T0 LUDLUM ELECTRIC FURNACE CORPORATION, OF WATERVLIET, NEW YORK, A CORPORATION OF NEW YORK.

. ELECTRIC FURNACE.

Specification of Letters Patent.

Patented Feb. 22, 1921.

Application filed October 1, 1919. Serial No. 327,706.

To all whom it may concern Be it known that 1, MAX It. Tnnnnoun, a citizen of theGerman Republic, residing at 108 Pinewoods avenue, in the city of Troy, county of Rensselaer, and State of New York, have invented certain new and useful Improvements in Electric Furnaces, of which the following is a specification. My present invention relates to electric furnaces, and particularly to the construction of the hearth of a furnace having a bottom connection, the object/ of my invention being to so construct the hearth that the current passes therethrough at a point at which repairs can be readily made, and preferably at a point such that the repairs can be made without pouring off the entire I charge, such for example as a point at or above the slag line.

In the accompanying drawings Figure 1 is a longitudinal section on the line 1-1 of Fig. 1 through a furnace in which my invention is embodied in one form; and a Fig. 2 is a transverse sectionon the line 2--2 of Fig. 1.

The present invention relates to electric furnaces of the bottom connection type, in which the current passes through the charge not only by way of electrodes above the charge, but also by way of the furnace hearth upon which the charge rests. It is particularly applicable to furnaces in which the charge is drawn off only partially, leaving a portion on the hearth to which the new metal is added in the cold state.

-In furnaces of this general type, it has heretofore been customary to' arrange the hearth conductors below the slag line in contact with the charge, and generally in the central part of the hearth. These conductors, if metallic, are customarily water cooled, or if non-metallic they generally consist of rammed and baked refractory materials, such as Irragnesite and dolomite. bonded by tar, which, while poor electrical conductors at low temperatures, carry current well at the high heat prevailing in the electric furnace.

The disadvantages of electric hearth connections are Well known to electric furnace operators. If the conductivity of the hearth is low and the resistance too high, suflicient heat may be generated to melt the hearth at short intervals, but where the melting is continuous, such inspection is impossible and the danger of a leak is greatly increased.

The present invention provides a construction which greatly diminishes these dangers. The construction is such that the current passes through the charge to or from. conductors placed in the furnace walls above the slag line or at points which can be inspected and reached for repairs without completely pouring off the charge. The

most suitable location is the furnace lining directly under the doors or the spout of the furnace. These points are easily accessible, and by tilting the furnace slightly in the proper direction, they can be inspected and repaired to a considerable distance below the normal slag line without pouring oil the charge. v

y The current. may be conducted to the charge by the usual means; either through the metallic shell, from there through metallic or carbonaceous conductors to the conducting heated refractory lining, and thence to the charge or directly through proper conductors (insulated from the shell) to the hot lining, and from there to the charge. However, instead of arranging the conductors leading to the lining directly underneath the hearth, they should be located in the side walls above the slag line or underneath the doors or spout as described above. This arrangement makes it possible to use carbonaceous conductors projecting to a. level with the rest of the furnace lining; in fact the entire sidewalls of the furnace above the slag line may be built of carbon bricks or may be rammed in with carbon and tar mixture, thus obtaining an excelof magnesite, dolomite, zirconite or other,

suitable refractories which at the high temperatures prevailing in a continuously operated furnace at all times. will carry the current to the charge easily and without undue resistance.

In case the metallic shell is not insulated from the electric conductors, care must be taken to insulate it electrically from the lower hearth to prevent metal, which might possibly work through small cracks in the lining, from coming into direct contact with the shell. A layer of asbestos board between the shell and brick work is usually sufficient for this purpose.

The current conducted to the charge through the bottom connection may represent one leg of a single or polyphase system, or with larger furnaces, it may represent the neutral of the system.

In the accompanying drawings I have shown the invention embodied in a furnace of the general type illustrated in my Patent No. 1,333,950 of March 16, 1920. In the present furnace, however, this metal shell 1 is insulated by layers of asbestos board 2 from the'hearth of the furnace. Directly beneath the doors or pouring spouts at opposite ends of the furnace, conducting material 3, such as carbon paste, is rammed directly upon the metal shell, or upon metal s ikes (not shown) fastened to the shell.

verlying this material and protecting it, is brick work 4, or the like, at or above the slag line of the charge 00, and consisting of carbonaceous bricks, or of bricks made of a conductor of the second class laid in carbon paste. The hearth proper 5, upon which the charge (17 lies, also consists of a conductor of the second class, such as magnesite, rammed upon a refractory brick lining 6, interposed between the hearth proper and the insulating sheathing 2 for the furnace shell 1. The power cable may be attached directly to the shell at 7, or at any other convenient location.

The adjustable top electrodes 8, 9 and 10 pass down through the removable roof 11 of the furnace and are connected in any suitable manner to the leads of the transformer. The hearth connection at 7 may be in parallel with one of the electrodes in a delta wound transformer, or to a neutral point in a star wound transformer.

The invention may be applied to furnacesof other types, and the construction may be varied in different embodiments without departing from what-I claim as my invention.

I claim v 1. An electric furnace comprising a hearth upon which the charge rests, top electrodes, at least certain of which are maintained in arcing relation to the charge during the op eration of the furnace, and an electrical connection to the marginal area of the hearth.

' 2. An electric furnace comprising a hearth upon which the charge rests, a pouring door above the normal slag level and through which access to the health may be had, and an electrical connection to the marginal area of the hearth adjacent said door.

3. An electric furnace comprising a tiltable hearth upon which the charge rests, a pouringdoor through which access to the hearth may be had, and an electrical connection to the hearth at a point accessible through said door for repairs while the charge is at least partially on the hearth.

4. An electric furnace comprising a hearth upon which the charge rests, and an electrical connection to the hearth in the region of the slag area of the charge.

5. An electric furnace comprising a hearth upon which the charge rests and tiltable to discharge the melt, and an electrical connection to the hearth above the normal slag level of the charge.

6. An electric furnace comprising a hearth upon which the charge rests, a furnace top, adjustable electrodes passing thercthrough to conduct current passing through the charge, and an electrical conrection from an element in the circuit of the top electrodes to the marginal area of the hearth.

7. An electric furnace comprising a tiltable hearth upon which the charge rests, a charging or discharging door through which access to the hearth may be had, and an electrical connection to the marginal area of the hearth above the normal slag level and in the region of said door.

In testimony whereof I have signed my name to this specification.

MAX R. TREMBOUR. 

